The present invention relates to a positive displacement viscous material pump assembly, and more particularly, to a viscous material pump assembly with three or more interconnected pumps.
In recent years, viscous material pumps (also referred to as sludge pumps or high solids material pumps) have found increasing use for conveying viscous material through a pipeline in municipal and industrial applications. Examples of viscous materials that can be conveyed with viscous material pumps includes thermally conditioned viscous material from clarifiers, filter cakes in food apparatus, flotation tailings in various mining operations, and bentonite-concrete mixtures for support extrusions.
In a typical viscous materials handling system, a feed system delivers material to a positive displacement pump which pumps the material to a disposal system. The feed system may include a belt press, an auger, a centrifuge or other devices for drying the material and delivering the material to the positive displacement pump. For example, in a viscous material application, the feed system may include a centrifuge or hopper, a screw feeder and a transition housing. The centrifuge dewaters and stores the viscous material prior to pumping. Once the viscous material has been dewatered, the centrifuge delivers the material to the screw feeder. The screw feeder, in turn, forces the viscous material through the transition housing into an inlet of the positive displacement pump.
The positive displacement pump can assume a variety of forms, but typically includes an inlet and one or more material cylinders which pump material to an outlet. Each material cylinder includes a material piston which is driven back and forth in a stroke cycle along a central axis of the material cylinder. During a fill stroke, the drive piston suctions material into the material cylinder. The material is expelled from the material cylinder to the outlet by a discharge or pumping stroke of the drive piston. The outlet is attached to the material disposal system. Typically, the material disposal system includes a lengthy outlet pipeline which terminates at a disposal device, such as an incinerator or containment pond. Alternatively, the material disposal system could include a truck which transports the pumped material to a remote area where it is spread out over the ground, subjected to further processing, etc.
Positive displacement viscous material pumps offer a number of significant advantages over alternative viscous materials handling systems, including screw or belt conveyers. Pumping viscous material through a pipeline contains odors for a safe and secure working environment. Viscous material pumps are capable of pumping thick, heavy sludges which may not be practical for belt or screw conveyers to transport. A pump and pipeline take up less space than a conveyer, and are capable of transporting material around corners with simple elbows. Viscous material pumps also offer reduction in noise over mechanical conveyers, and generally offer greater cleanliness and no spillage.
Multiple positive displacement viscous material pumps may be necessary for large volume applications such as pumping mine tailings. However, simultaneous discharge by all the pumps into the outlet pipeline can have substantial negative effects including massive pressure spikes within the outlet pipeline. The pressure spikes can lead to viscous material backing up into the pumps, or in extreme cases, pipeline or pump failure. Additionally, the physical arrangement and operation of multiple viscous material pumps can negatively affect the fill efficiency of some or all of the pumps due to variations in the amount of viscous material entering the cylinders of each pump. Poor pump fill efficiency is known to lead to cavitation during the pump's discharge stroke, thus increasing pump wear.